CYCLES. 109 
The agreement seems to the writer to justify the conclusion that 
the tree record may indicate a possible sunspot period of 11.3 years 
from 1400 to 1550 and of 14.3 from the latter date to 1600. 
Sequoia pattern.—Pattern B in plate 10, opposite page 94, is naturally 
the most interesting in respect to age, as it gives the sequoia analysis 
for 3,200 years. The solar cycle subject to slight variations may be 
dimly seen in large parts of it. It shows with some prominence during 
the first 500 years of our era, then for a few hundred years near the 
year 1000 A. D., and for a long interval in the first 500 years of the 
record. There is opportunity for extensive study of these short periods, 
interpreting them by the aid of more widely scattered groups and other 
kinds of trees, and when possible by weather records. 
ot HBS 
7850 AP: 
so 60 70 80 90 100 NOs 120 130 
100 90 80 7O 60 50 40 30 
30 40 50 60 70 80 90 100 
Fie. 40.—T wo differential patterns of Huntington’s preliminary 2000-year sequoia record. The 
most prominent cycle is about 105 years in length, shown in the upper diagram. 
Other solar cycles.—Plate 12, a to p, shows the multiples of the solar 
cycle. Pattern G gives the Arizona tree record analyzed at 23.5 years. 
It shows a slightly irregular vertical row of crests. This is best seen by 
tipping the pattern so that the eye views it from a low angle instead of 
perpendicularly as in ordinary reading. A line slanting down to the 
left giving a period at nearly 22.2 years would answer quite as well. 
The lower third is somewhat broken by the triple sunspot period 
showing in it. The same record is analyzed at 33.0 years in pattern 
N. In this pattern the lower third shows the triple cycle in vertical 
rows and the double cycle shows in rows slanting strongly down to the 
left. Patterns H and J in plate 12 show the excellent double sunspot 
